The research program has the objectives of elucidating the primary responses of procaryotic and eucaryotic cells to lead in an attempt to define trace mechanisms of action. With the lead-treated bacterium, Micrococcus luteus there is a two-fold approach to identifying the bases for the observed sharp reduction in total cellular lipids: 1) effects of lead on depolymerization of ribosomes, and 2) effects of lead on neutral lipid synthesis as they serve as precursors to polar lipid synthesis. Investigations are also being conducted on the nature of the bacterial resistance to effects of lead. These studies are being approached on the bases of the possible occurrence of genetic resistant factors. In studies on the effects of lead on eucaryotic systems, efforts are directed towards the pulmonary system. The emphasis is on the effect of the inciting agent on lipid synthesis and total lipid content of lungs, surfactant, lamellar bodies, and alveolar macrophages. These studies are accompanied with ultrastructural examinations by transmission electron-, transmission electron-x-ray spectrometry-, and scanning electron-microscopy.